Hi, you're code:

if ( $Lines eq "<NumberofDays>\d+</NumberofDays>" )
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should be something like:

if ( $Lines =~ m|<NumberofDays>(\d+)</NumberofDays>| )
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3 differences between your and my line:

• eq vs. =~
to compare against a regular expression you use =~
• the regular expression is in 'm|' and '|' characters
This is to make clear you are using a regular expression
• the \d+ is in '(' and ')' characters
This is used to 'capture' the value of the expression inbetween them. In this case it would capture the value in $1. The rule is the first ()-match is captured in $1, the second in $2 etc. So in your code you could continue with something like

print $1
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Hope this helps getting you started. For documentation on regular expressions there are 2 good tutorials that come with perl that were not mentioned here: perlrequick perlretut